Protective Effects of Different Egg Yolk Sources on Cryopreservation of Scaly Carp (Cyprinus carpio) Sperm

Abstract

Egg yolk is one of the most widely used cryoprotective components of extenders, especially for the cryopreservation of mammalian species’ sperm cells. However, there is a lack of information regarding their efficacy in cryopreservation of fish sperm cells. Thus, the objective of this experiment was to compare the effectiveness of egg yolk from different avian species (duck, goose, and chicken) on post-thaw quality and fertilization ability of scaly carp (Cyprinus carpio) semen following cryopreservation. Sperm samples diluted with the sucrose-based extender at the ratio of 1:10 were supplemented with 10, 15, and 20% ratios of different avian egg yolks. In the control group, sperm samples were diluted with the sucrose-based extender, without egg yolk. Following dilution, sperm samples were equilibrated at +4⁰C for 10 min and aspirated into 0.25-ml straws. Then, sperm samples were frozen 3 cm above the liquid nitrogen (LN2) surface and plunged directly into the LN2. The frozen sperm cells were thawed in a water bath at 35 ⁰C for 30 s and fertilization was carried out using a 1x105 spermatozoa/egg ratio. Based on the results, supplementation of sperm cells with 20 % duck egg yolk in a sucrose-based extender exhibited the best post-thaw progressive motility (67.8 ±1.24%), progressive motility duration (32.6 ±1.45 s), viability (82.4 ±1.36%), and fertility (92.6 ±1.28%) compared to the control group (P<0.05). The results of the experiment showed that duck egg yolk could be used as an alternative instead of chicken egg yolk in a sucrose-based extender for the cryopreservation of scaly carp sperm.